Theoretical insight into H2O impact on V2O5/TiO2 catalysts for selective catalytic reduction of NOx.

H2O in flue gas causes the deactivation of V2O5/TiO2 catalysts for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Developing water resistance requires understanding the theoretical mechanism of H2O impact on the catalysts. The aim of this work was to clarify the adsorption process of H2O and the deactivation mechanism induced by H2O through density functional theory (DFT). The process of H2O adsorption was studied based on a modeled V2O5/TiO2 catalyst surface. It was found that H2O had a strong interaction with exposed titanium atoms. Water adsorption on the catalyst surface significantly alters the electronic structure of VOx sites, transforming Lewis acid sites into Brønsted acid sites. Exposed titanium sites contribute to the decrease of Lewis acidity via adsorbed water. Ab initio thermodynamic calculations show that H2O adsorption on V2O5/TiO2 is stable at low coverage but less favorable at high coverage. Adsorption of NH3 is the most critical step for the SCR of NOx, and the adsorption of H2O can hinder this process. The H2O coverage below 15% of adsorption sites could enhance the NH3 adsorption rate and have a limited effect on the acidity, while higher coverage impeded the adsorption ability of VOx sites. This work provided electron-scale insight into the adsorption impact of H2O on the surface of V2O5/TiO2 catalysts, presented thermodynamic analysis of the adsorption of H2O and NH3, paving the way for the exploration of V2O5/TiO2 catalysts with improved water resistance.

Reduction of heavy metals in municipal solid waste incineration fly ash followed by making transparent glass.

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste containing heavy metals. Secondary aluminum dross (SAD) is a hazardous waste discharged from aluminum smelting, containing active aluminum nitride (AlN). In this work, heavy metals from MSWI fly ash were reduced into alloy by AlN from SAD, and the slag was manufactured into transparent glass for building. Reduction of iron and zinc was 67 and 100 %, respectively. Reduction mechanism was explored after applying XRD, XRF and thermodynamics analysis. It was found that the reduction reaction was an ion reaction. The AlN and heavy metal oxide transformed into anionic group containing nitrogen and heavy metal cation, after entering slag. The heavy metals were reduced into alloy after electron was transferred from anionic group to cation. In addition, the reduced iron and zinc could merge into alloy, which inhibited evaporation of zinc. Yellow transparent glass was obtained after the reduction process. Yellow was come from titanium oxide, which could not be reduced by AlN. Microhardness, density and water absorption of the transparent glass were 741 HV, 2.86 g·cm-3 and 0.04 %, respectively. Leaching content of Ni, Cu, Zn and Pb of the glass were 0.1, <0.1, 0.6 and < 0.1 mg/L, respectively, all below the TCLP limit. About 115 âˆ¼ 213 dollars were earned after manufacturing 500 kg of MSWI fly ash into transparent glass. This work provided a novel idea of recycling solid waste into alloy and transparent glass for building.

Optimization of synergistic capturing platinum group metals by Fe-Sn and its mechanism.

Platinum group metals (PGMs) are strategic metals. Auto-exhaust catalysts are their main application fields. The recovery of PGMs from spent auto-exhaust catalysts has remarkable economic value and strategic significance. Aiming at the problems of ferrosilicon generation for Fe capturing and subsequent oxygen blowing to remove iron with high energy consumption and heat release, a technology of Fe-Sn synergistic capturing PGMs was proposed. Taking full the advantage of the lower melting point of Fe-Sn alloy (<1200 °C) and its unique affinity for PGMs, the PGMs were captured at approximate 1400 °C with Fe-Sn as the collector. In experiment, 500 g of spent auto-exhaust catalysts were employed to minimize error and approximate industrial production. The mechanism of Fe-Sn synergistic capturing PGMs was elucidated. The generation of Fe-Sn-PGMs alloy lowered the activity of [PGMs] in the system, accelerated the reduction of the PGMs oxides and promoted the alloying of [PGMs]. Therefore, Fe-Sn synergistic capturing PGMs was realized. The inability of Si to enter the alloy phase was confirmed by theoretical calculations, avoiding the generation of ferrosilicon. The effects of basicity, CaF2, m(Fe)/m(Sn) and the amount of collector on capturing PGMs were optimized. Under the optimized conditions (basicity R = 1.1, spent auto-exhaust catalysts 70 wt%, CaO 30 wt%, B2O3 10 wt%, CaF2 7 wt%, m(Fe)/m(Sn) = 1/1 and the collector 15 wt%), the content of PGMs in the slag phase was 2.46 g/t. It is feasible to remove Fe and Sn by oxidation to achieve the purpose of PGMs enrichment. This technology offers guidance on the safe, environmentally sound, and efficient disposal of spent auto-exhaust catalysts, promoting the sustainable development of PGMs.

Efficient and comprehensive recycling of valuable components from scrapped Si-based photovoltaic panels.

The increasing scrapped Si-based photovoltaic (PV) panels has become an urgent problem, and their disposal is essential for resources utilization and environment issues. This paper proposes a comprehensive process for recycling of discarded silicon-based PV panels economically, environmentally, and efficiently. Based on the thermal properties of ethylene vinyl acetate (EVA), they are removed from the discarded PV panels at 600 °C with heating rate of 5 °C/min and maintain for one hour. The glass, solar cells, and copper strips were separated after heat treatment. Simultaneously, the solar cells were crushed into powder. Nitric acid was used to recover silver from the solar cell powder, while most of the metal impurities such as Mg, Ti and Al, were removed as well. The leaching efficiency of silver was over 96 % under the optimized conditions: HNO3 of 4.0 mol/L, liquid-to-solid ratio of 10:1, temperature of 50 °C for 80 min. Regarding the copper strips, they were sequentially treated with 0.5 mol/L CH3COOH and NaOH solution to remove the oxides of Pb and Sn on their surface. Subsequently, they were placed into the solution of 1.0 mol/L CuSO4 with pH of 2 âˆ¼ 3 to eliminate Pb and Sn. This article provides significant reference for the recycling of Si-based PV panels.

A review of biomineralization in healing concrete: Mechanism, biodiversity, and application.

Concrete is the main ingredient in construction, but it inevitably fractures during its service life, requiring a large amount of cement and aggregate for maintenance. Concrete healing through biomineralization can repair cracks and improve the durability of concrete, which is conducive to saving raw materials and reducing carbon emissions. This paper reviews the biodiversity of microorganisms capable of precipitating mineralization to repair the concrete and their mineralization ability under different conditions. To better understand the mass transfer process of precipitates, two biomineralization mechanisms, microbially-controlled mineralization and microbially-induced mineralization, have been briefly described. The application of microorganisms in the field of healing concrete, comprising passive healing and intrinsic healing, is discussed. The key insight on the interaction between cementitious materials and microorganisms is the main approach for developing novel self-healing concrete in the future to improve the corrosion resistance of concrete. At the same time, the limitations and challenges are also pointed out.

Fast inverse lithography approach based on a model-driven graph convolutional network.

Inverse lithography technique (ILT) is a leading-edge method to improve the image fidelity of an advanced optical lithography system by performing pixel-wise optimization on the transmission function of photomask. However, traditional ILTs are computationally intensive, which limits their application in high volume manufacturing of integrated circuits. This paper proposes a model-driven graph convolutional network (MGCN) framework combined with the dense concentric circular sampling (DCCS) method to effectively improve computational efficiency and imaging fidelity of current ILTs. Firstly, the DCCS template is used to extract the geometric features from the layout pattern of integrated circuits, which are then input into a GCN-based encoder to predict the optimized mask pattern of the ILT. Then, a model-driven decoder based on the lithography imaging process is developed to retrieve the print image of the predicted ILT mask. By means of the cooperation between the encoder and decoder, an unsupervised training strategy is proposed to avoid the time-consuming labelling process of the training samples. With the help of the parallel computing under GPU framework, the well-trained encoder can make a fast prediction of ILT mask with high-fidelity image results. The results demonstrate the state-of-the-art performance of the proposed MGCN approach compared to some other comparative ILT methods.

Co-vitrification of municipal solid waste incinerator fly ash and bottom slag: Glass detoxifying characteristics and porous reformation.

Safety and efficient dispose of municipal solid waste incineration (MSWI) fly ash with high toxicity has emerged as a worldwide challenge. Vitrification provides the advantages of capacity reduction, detoxification, and solidification of heavy metals, which has the potential to dispose of hazardous waste on a large scale. Herein, co-vitrification of MSWI fly ash and bottom slag has been accomplished based on the characteristics of calcium and silicon composition. A novel approach for producing glass ceramic foams by alkaline activation-crystallization was developed to realize the disposal of the obtained glass. The effect of MSWI fly ash/bottom slag ratios on the glass network, crystallization ability of the basic glass, pore structure, and physical properties of the porous green body was investigated. The results revealed that with increasing MSWI fly ash proportion, the Si-O of [SiO4] in the basic glass changed significantly and the crystallization ability steadily reduced. Si-O and Al-O in basic glass are easy to corrode under alkaline conditions, releasing Ca2+ and forming a low solubility product, calcium silicate hydrate. When the crystallization temperature increases from 950 â„ƒ to 1150 â„ƒ, it is more conducive to the precipitation of the gehlenite phase. Extending the crystallization time promotes three-dimensional growth of crystals that are coupled with each other to form a network structure and a multi-stage pore structure. The pore structure was developed with the help of NH3 and H2 generated by the secondary aluminum ash (SAA). Through the preparation of glass ceramic foams, the raw materials were detoxified. The toxic heavy metals showed extremely low leaching concentrations, which were smaller than the limit of TCLP. The prepared samples had 70.22-80.61% of porosity, 0.78-1.19 g/cm3 of low bulk density, and 0.54-7.86 MPa of compressive strength.

Slag design and iron capture mechanism for recovering low-grade Pt, Pd, and Rh from leaching residue of spent auto-exhaust catalysts.

Recovery of platinum group metals (PGMs) from secondary resources has attracted worldwide attention from environmental and economic points of view. Pyrometallurgical routes exhibit the superiority in terms of efficiency and contamination control compared to hydrometallurgical process. However, traditional pyrometallurgical processes face the challenges of excessive flux and energy consumption. In this paper, an iron capture process was proposed to recover low-grade PGMs from leaching residue of spent auto-exhaust catalysts. Slag design was explored aimed at reducing the addition amount of flux. The optimized smelting conditions were as follows: 1400 °C for 30 min, adding 40.0 wt% CaO, 22.7 wt% Na2CO3, 5.0 wt% Na2B4O7, 5.0 wt% CaF2, 15.0 wt% Fe, and 5.0 wt% C. The concentrations of Pt, Pd and Rh remaining in the smelting slag were 0.83 g/t, 4.99 g/t, and 1.47 g/t, respectively. Furthermore, the 50 kg-scale experiment implied positive economic feasibility because of saving flux dosage and smelting time. The capture mechanism was revealed by investigating the formation of the metals phase and slag phase. Matrix formed slag phase and separate with metals phase owing to differences in chemical bonding, density, viscosity, and surface tension. PGMs were proved solubilized in α-Fe as substitutional solid solutions. The formation energies for FePt, FePd, and FeRh alloys were -4.149 eV, -4.040 eV, and -4.360 eV, respectively. Finally, the obtained CaO-SiO2-Al2O3-Na2O glass slag was used for producing glass ceramics. To sum up, the iron capture process realized low energy and material consumption, high recovery efficiency of PGMs, and resource utilization of the glass slag.

Efficient informatics-based source and mask optimization for optical lithography.

Source and mask optimization (SMO) is a widely used computational lithography technology that greatly improves the image fidelity of lithography systems. This paper develops an efficient informatics-based SMO (EISMO) method to improve the image fidelity of lithography systems. First, a communication channel model is established to depict the mechanism of information transmission in the SMO framework, where the source is obtained from the gradient-based SMO algorithm. The manufacturing-aware mask distribution is then optimized to achieve the best mutual information, and the theoretical lower bound of lithography patterning error is obtained. Subsequently, an efficient informatics-based method is proposed to refine the mask optimization result in SMO, further reducing the lithography patterning error. It is shown that the proposed EISMO method is computationally efficient and can achieve superior imaging performance over the conventional SMO method.

Reduction for heavy metals in pickling sludge with aluminum nitride in secondary aluminum dross by pyrometallurgy, followed by glass ceramics manufacture.

Secondary aluminum dross (SAD) from aluminum industry is classified as a hazardous solid waste due to containing aluminum nitride (AlN). In this work, AlN was first used to reduce heavy metals by pyrometallurgy. The reduction rates for iron, chromium and nickel were up to 90%, 80% and 100%, respectively. However, the reduction from AlN and oxygen oxidization of AlN occurred simultaneously. AlN which formed solid solution with alumina could reduce heavy metals, while the rest was oxidized by oxygen. In addition, the reduction rates for iron and chromium could be increased with increasing CaF2 from 6.7 to 9.0 wt%. CaF2 could decreased viscosity of molten slag, which favored the ion migration, and then increased the reduction rates. After the reduction, glass ceramics were manufactured from the molten slags. The bending strength, microhardness and alkali resistance of the glass ceramics were up to 77 MPa, 1011 HV and 98.7%, respectively. According to XRD and SEM results, glass ceramics with CaAl2SiO6 crystal phase, crosslinked network structure grains and smaller pores exhibited better bending resistance. In addition, glass ceramics with CaAl2SiO6 crystal phase possessed the highest microhardness and alkali resistance. After this process, hazardous pickling sludge and SAD were totally recycled.

Three-Dimensional Reticulated, Spongelike, Resilient Aerogels Assembled by SiC/Si3N4 Nanowires.

For nanofibrous aerogels, a three-dimensional porous structure with interwoven nanofibers as a pore wall has become an urgent demand, and it remains to be a challenge to ensure the mechanical stability and thermal insulation. Other than the reported nanofiber as raw materials to generate three-dimensional cellular nanofibrous aerogels, an alternative low-cost and facile procedure has been proposed here via tactfully utilizing polymer sponge as a template attached with reactive particles, followed by a carbothermal reduction process to realize nanowire growth and their replacement of the original framework. The resulting spongy aerogels with numerous interlaced SiC/Si3N4 nanowires as a skeleton exhibit an ultrahigh porosity of 99.79%. Meanwhile, compressive elasticity after a compression at strain of 35% for 400 cycles, a low thermal conductivity of 23.19 mW/(m K), an excellent absorption capacity of 33.9-95.3 times for varied organic solvents removal, along with flexibility in shape design favored by the initial organic sponge make this nanofibrous aerogel an ideal material for heat shielding, absorption, or catalyst support.

A review of glass ceramic foams prepared from solid wastes: Processing, heavy-metal solidification and volatilization, applications.

The safe utilization of solid wastes containing heavy metals plays a crucial role in environmental preservation. As an efficient technology to achieve this goal, the preparation of glass ceramic foams from solid wastes can produce an excellent solidification effect on heavy metals. At present, there have been plenty of efforts made to achieve an excellent combination of such characteristics as mechanical strength, bulk density, thermal conductivity and so on, with the purpose to ensure the application in various high value-added fields. Due to the concentration on their application in the construction sector such as the use of thermal and acoustic insulation materials, some researchers seek to expand the scope of their applications. In this paper, a review is conducted into the methods used to prepare solid waste-based glass ceramic foams. Depending on the exact processing route, these methods can be categorized into two classes, which are powder sintering and inorganic gel casting. Not only heavy metals hinder the application of solid waste, they can also cause irreversible pollution to the wider environment. Solidification and volatilization represent the two routes associated with heavy-metal migration during the preparation of glass ceramic foams. Both traditional and innovative applications are indicated in this review. Furthermore, a discussion is conducted about the prospects and challenges facing different processing strategies, heavy-metal migration and applications.

Harmless disposal and resource utilization for secondary aluminum dross: A review.

Secondary aluminum dross (SAD) is solid waste of primary aluminum dross extracted aluminum, which contains approximately 40-60 wt% alumina, 10-30 wt% aluminum nitride (AlN), 5-15 wt% salts and other components. The salts include sodium chloride, potassium chloride and fluorine salts. SAD has dual attributes as resource and pollutant. SAD landfill disposal has the disadvantages of occupying land, wasting resources, a high cost and great environmental impact. SAD utilization methods are currently pyrometallurgy and hydrometallurgy. In pyrometallurgy, AlN is oxidized and the salts are evaporated at high temperature. After mixing, molding and calcination, firebricks and ceramics can be manufactured from SAD. In hydrometallurgy, AlN is hydrolyzed and salts are dissolved in water. After dissolving, filtrating, precipitating, washing and calcination, γ-Al2O3 can be prepared from SAD. Resource consumption and emission from both utilization methods were assessed. A ton of magnesium aluminum titanate based ceramics by pyrometallurgy consumes 1043 kg raw materials and releases 69 kg of waste gas, 4.17 t of waste water and no solid waste. A ton of γ-Al2O3 by hydrometallurgy consumes 3389 kg raw materials and releases 111 kg of waste gas, 12.98 t of waste water and 267 kg of solid waste. Therefore, the resource consumption and emission of SAD utilization by pyrometallurgy is lower than that by hydrometallurgy. We should focus on reducing the emission of the three wastes from pyrometallurgy. We are sure that SAD can be utilized for glass ceramics by pyrometallurgy. AlN and salts can be transformed into alumina and glass phases at high temperature with no emission. We should clarify mechanisms for SAD composition adjustment to lower the glass ceramics' melting point, AlN and salts transformed into alumina and glass phases respectively, and nucleation and crystal growth of glass ceramics at high temperature.

Emerging pollutants-Part II: Treatment.

Emerging pollutants (EPs) refer to a class of pollutants, which are emerging in the environment or recently attracted attention. EPs mainly include pharmaceutical and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), and antibiotic resistance genes (ARGs). EPs have potential threats to human health and ecological environment. In recent years, the continuous detections of EPs in surface and ground water have brought huge challenges to water treatment and also made the treatment of EPs become an international research hotspot. This paper summarizes some research results on EPs treatment published in 2019. This paper may be helpful to understand the current situations and development trends of EP treatment technologies.

Nonlinear compressive inverse lithography aided by low-rank regularization.

Photolithography is at the core of the semiconductor industry that is used to fabricate microscale and nanoscale integrated circuits. Inverse lithography is a technique extensively used to compensate for lithography patterning distortions. It refers to methods that pre-distort the photomask patterns such that their projection, through the photolithography system, results in a pattern that is as close as possible to the intended original. However, most inverse lithography technique (ILT) methods suffer from large computational complexity. This paper develops a nonlinear compressive sensing framework for ILT that effectively improves the computational efficiency and image fidelity, while at the same time controlling the mask complexity. Based on a nonlinear lithography imaging model, the compressive ILT is formulated as an inverse optimization problem aimed at reducing the patterning error, and enforcing the sparsity and low rank properties of the mask pattern. A downsampling strategy is adopted to reduce the dimensionality of the cost function, thus alleviating the computational burden. Sparsity and low-rank regularizations are then used to constrain the solution space and reduce the mask complexity. The split Bregman algorithm is used to solve for the inverse optimization problem. The superiority of the proposed method is verified by a set of simulations and comparison to traditional ILT algorithms.

Emerging pollutants-Part II: Treatment.

Recently, emerging pollutants (EPs) have been frequently detected in urban wastewater, surface water, drinking water, and other water bodies. EPs mainly usually include pharmaceuticals and personal care products, endocrine-disrupting chemicals, antibiotic resistance genes, persistent organic pollutants, disinfection by-products, and other industrial chemicals. The potential threat of EPs to ecosystems and human health has attracted worldwide attention. Therefore, how to treat EPs in various water bodies has become one of the research priorities. In this paper, some research results on treatment of EPs published in 2018 were summarized. PRACTITIONER POINTS: At present, more attention has been paid to emerging pollutants (EPs), including pharmaceuticals and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), antibiotic resistance genes, persistent organic pollutants, disinfection by-products, etc. Existing EPs disposal technologies mainly include: engineered wetlands and natural systems, biological treatment, physical and physicochemical separation, chemical oxidation, catalysis, etc. This paper reviews some research results on the treatment technologies of EPs published in 2018.

An Efficient Leaching of Palladium from Spent Catalysts through Oxidation with Fe(III).

Reclamation of spent catalysts for the efficient recovery of palladium (Pd) is gaining growing attention due to its scarcity and high supply risk. Currently Pd extraction from spent catalysts through an efficient, economical, and green method has remained a challenge. In this study, Fe3+ is utilized for leaching through oxidation of Pd in a mild condition. Before leaching, distillation was proposed to remove and recover the organics from spent catalysts. The effects of HCl concentration, Fe3+ concentration, NaCl concentration, leaching time, and temperature on the leaching efficiency of Pd were investigated to determine the optimum leaching conditions. The results show that Pd extraction and dissolution of Al2O3 increase with higher HCl concentration. The effect of NaCl on Pd leaching efficiency is significant at low acid concentration (2.0 mol/L HCl). The leaching efficiency was 99.5% for Pd under the following conditions: 2.0 mol/L HCl, 4.0 mol/L NaCl, and 0.67 mol/L Fe3+ at 80 °C for 90 min. The leaching kinetics fits best to the shrinking-core model of surface chemical reaction. The activation energy for the leaching of Pd was 47.6 kJ/mol. PdCl42- was selectively adsorbed by anion exchange resin. The filtrate containing adequate H+, Cl-, and Fe3+ was reused as leaching agent. Pd leaching efficiency was over 96% after five cycle times. This study provides an efficient process for recovery of Pd from spent catalysts.

Controlling the Composition and Magnetic Properties of Nano-SrFe12O19 Powder Synthesized from Oily Cold Mill Sludge by the Citrate Precursor Method.

This paper proposes a new method for producing nano-SrFe12O19 powder by the citrate precursor route using solid waste as a source of iron. This solid iron-containing waste, which exists in the form of an oily sludge, is produced by a cold rolling mill. This sludge was first subjected to a process, including sulfuric acid leaching, oxidation, precipitation, and nitric acid leaching, to obtain an iron nitrate (Fe(NO3)3) solution. Next, the Fe(NO3)3 solution was mixed with a strontium nitrate (Sr(NO3)2) solution obtained by subjecting strontium carbonate to nitric acid leaching. Subsequently, citric acid, as chelating agent, and ammonia water, as precipitating agent, were added to the mixed solution to form a gel. The gel was dried and spontaneously combusted, then annealed at different temperatures for 2 h in flowing air. The effects of the Fe3+/Sr2+ molar ratio and annealing temperature on the formation, morphology, and magnetic properties of SrFe12O19 were investigated. The results showed that single-phase SrFe12O19 powder was obtained by decreasing the Fe3+/Sr2+ molar ratio from the stoichiometric value of 12 to 11.6 and increasing the annealing temperature to 1000 °C for 2 h. Adjustment of the Fe/Sr molar ratio to 12 and the annealing temperature to 900 °C enabled the magnetic properties to be optimized, including saturation magnetization (Ms) 80.2 emu/g, remanence magnetization (Mr) 39.8 emu/g, and coercive force (Hc) 6318 Oe.

Emerging Pollutants - Part II: Treatment.

Emerging pollutants (EPs) are a class of chemical pollutants that have potential or substantial threats to human health and ecological environment. EPs mainly include pharmaceuticals and personal care products, endocrine disrupting chemicals, antibiotics, persistent organic pollutants, disinfection by-products and other industrial chemicals, etc. In recent years, with the improvement of environmental analysis level, these substances have been detected frequently in urban sewage, surface water and drinking water all over the world. The continuous detection of EPs brings new challenges to water pollution control, and also makes EPs treatment an international research hotspot. This paper summarizes some research results on emerging pollutants treatment published in 2017.

The region-specific segregation and catalytic activity of gold-silver nanoparticles.

A coordination-dependent interatomic interaction is developed for Ag atoms and applied to simulate Au-Ag alloy nanoparticles ranging from 2.6 nm to 4.5 nm with different composition ratios at different temperatures. Using the lattice Monte Carlo method, we found that Ag segregates preferentially on the edges of nanoparticles. The region-specific segregation is revealed by our study and it indicates that depending on the size and temperature, Ag may segregate on the edges only, whereas its segregation on flat surfaces is negligible. Assuming that equimolar Au-Ag edges maximize the catalytic synergistic effect, we predicted the size and composition dependent optimal reaction temperatures for the Au-Ag catalyzed CO oxidation, which agree with the available experimental temperatures very well. Our study demonstrates that the region-specific segregation not only complements the details of surface segregation but is also very important for the utilization and tuning of faceted bimetallic nanoparticles.